netdev - Re: [PATCH net-next] fib_hash: embed initial hash table in fn

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Message-ID: <1287084159.2659.0.camel@edumazet-laptop>
Date:	Thu, 14 Oct 2010 21:22:39 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] fib_hash: embed initial hash table in fn_zone

Le jeudi 14 octobre 2010 à 18:24 +0200, Eric Dumazet a écrit :
> While looking for false sharing problems, I noticed 
> sizeof(struct fn_zone) was small (28 bytes) and possibly sharing a cache
> line with an often written kernel structure.
> 
> Most of the time, fn_zone uses its initial hash table of 16 slots.
> 
> We can avoid the false sharing problem by embedding this initial hash
> table in fn_zone itself, so that sizeof(fn_zone) > L1_CACHE_BYTES
> 
> We did a similar optimization in commit a6501e080c (Reduce memory needs
> and speedup lookups)
> 
> Add a fz_revorder field to speedup fn_hash() a bit.
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>

Oops, a last minute change was wrong, I'll resend a V2.

Thanks


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